Feasibility of lung cancer hyperthermia using breathable perfluorochemical (PFC) liquids. Part I: Convective hyperthermia.

Clinical studies have shown that hyperthermia in combination with radiotherapy and/or chemotherapy may be effective in the treatment of advanced cancer. No method of lung hyperthermia, however, has been accepted as standard or superior. This investigation sought to demonstrate in animals the thermal and physiologic feasibility of lung hyperthermia induced using heated breathable perfluorochemical (PFC) liquids, a method termed liquid-filled lung convective hyperthermia (LCHT). The ability to use LCHT is rooted in the development of both PFC liquid ventilation, now in clinical development with the PFC perflubron (LiquiVent), and a PFC blood substitute also in late Phase III trials (Oxygent). As LCHT background, the PFC technologies and biology are first reviewed. The physical properties of a variety of PFCs were evaluated for LCHT and it was concluded that more than one liquid is suitable based on such properties. Using total liquid ventilation type devices, LCHT was shown to deliver successfully localized (lobar) lung heating in sheep, and bilateral whole lung heating and whole-body hyperthermia in rabbits, cats and lambs. During LCHT, lung parenchymal temperatures were uniform (<1 degree C) across heated regions. In addition, based on patterns relating lung tissue temperatures to inspiratory and expiratory PFC liquid temperatures in the endotracheal tube, LCHT may minimize invasive thermometry requirements in the lung. Based on acute experiments, it was concluded that LCHT appears feasible and may simplify lung hyperthermia. It was recommended that potentially synergistic combinations of LCHT with other whole-body hyperthermia or local heating modalities, and with chemotherapeutic lung drug delivery, also be explored in the future.

Quercetin sensitizes cells in a tumour-like low pH environment to hyperthermia.

Quercetin has been shown to act as a hyperthermia sensitizer by inhibiting the synthesis of heat shock protein 70 (HSP70) in a variety of tumour cell lines. It is most effective under conditions of low pH. This study was designed to test the hypothesis that quercetin suppresses thermotolerance development in cells adapted to growth at low pH and renders them as responsive as acutely acidified cells to hyperthermia-induced cytotoxicity. Chinese hamster ovarian carcinoma cells (OvCa) were exposed to 42 degrees C hyperthermia and/or quercetin (50-200 mm) at their growth pH of either 7.3 or 6.7 or after acute acidification from 7.3 to 6.7. Thermotolerance development was measured by colony survival. HSP70 synthesis and total protein synthesis were measured by radioactive precursor pulse labelling techniques. Quercetin, in a concentration-dependent manner, reduced the rate of total protein synthesis and increased cytotoxicity equally after acute acidification to pH 6.7 or growth at pH 6.7 at 37 degrees C, and to a greater extent than it did in cells at pH 7.3. At 42 degrees C, 100 mm quercetin inhibited total protein synthesis, HSP70 synthesis and thermotolerance development to a similar extent in cells grown at pH 6.7 or acutely acidified to pH 6.7. In contrast, quercetin reduced but did not completely inhibit HSP70 synthesis and thermotolerance development in cells grown and heated at pH 7.3. These results support the hypothesis that quercetin can specifically reduce thermotolerance development in tumour cells adapted to growth at pHe 6.7 so that they respond similarly to acutely acidified cells. Since many tumours are adapted to growth at low pH and may resist a wide variety of therapeutic modalities, inhibition of thermotolerance expression by quercetin may not only enhance the response to hyperthermia but the response to commonly used therapies such as chemotherapy and radiation.

Acute extracellular acidification increases nuclear associated protein levels in human melanoma cells during 42 degrees C hyperthermia and enhances cell killing.

Acute acidification is being investigated as a strategy to sensitize human melanoma to 42 degrees C hyperthermia. The present study was conducted to determine the effect of hyperthermia and acute extracellular acidification on the nuclear associated protein (NAP) levels, heat shock protein (hsp) 70 and hsp27 content, and cell survival of human melanoma cells cultured at pH 7.3 or pH 6.7. It was observed that NAP levels increased slightly in both populations after 2 h of heating and then decreased to control levels with increasing time of heating at the growth pH. However, the NAP levels continued to increase in cells acutely acidified to pH 6.3 prior to and during heating. Hsp70 was induced to comparable levels in cells heated at their growth pH; however, the hsp27 levels were greater in cells cultured and heated at pH 6.7 than in cells cultured and heated at pH 7.3. Acute acidification to pH 6.3 prior to and during heating suppressed the 42 degrees C induction of hsp70 and hsp27 in both cell populations. The melanoma cells cultured and heated at pH 6.7 were more resistant to cell killing than cells cultured and heated at pH 7.3. Both populations were sensitized to cell killing by acute acidification to pH 6.3. The results suggest that hsps induced during 42 degrees C treatment associate with aggregating NAPs, enhancing their detergent solubility, and that abrogation of induced expression of hsps during heating at pH 6.3 contributes to increased levels of insoluble NAPS. In conclusion, acute extracellular acidification inhibits 42 degrees C induction of hsps, increases NAP levels, and decreases cell survival in DB-1 human melanoma cells.

Non-invasive magnetic resonance thermometry using thulium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (TmDOTA(-)).

Non-invasive thermometry is pivotal to the future advances of regional hyperthermia as a cancer treatment modality. Current magnetic resonance (MR) thermometry methods suffer from poor thermal resolution due to relatively weak dependence of chemical shift of the (1)H water signal on temperature. This study evaluated the feasibility of using thulium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (TmDOTA(-)) for MR thermometry. TmDOTA(-) is non-toxic and the gadolinium complex of DOTA(4-) is widely used as a MR contrast agent. The results demonstrate that the temperature dependence of the TmDOTA(-) proton shifts are about two orders of magnitudes higher than the water proton and, thus, provide excellent accuracy and resolution. In addition, TmDOTA(-) proton shifts are insensitive to the paramagnetic complex concentration, pH, Ca(2+) or presence of plasma macromolecules and ions. Because hyperthermia is known to produce changes in tissue pH and other physiological parameters, these properties of TmDOTA(-) greatly simplify the procedures for using the lanthanide complex for MR thermometry. Application of TmDOTA(-) for measurement of temperature in a subcutaneously implanted human melanoma xenograft is demonstrated. Finally, the feasibility of imaging one of the (1)H resonances of the lanthanide complex is demonstrated in phantom experiments. Overall, TmDOTA(-) appears to be a promising probe for MR thermometry in vivo.

Betulinic acid sensitization of low pH adapted human melanoma cells to hyperthermia.

Betulinic acid is a known inducer of apoptosis in human melanoma that is most effective under conditions of low pH. It was hypothesized that betulinic acid, in combination with acute acidification and/or hyperthermia, would induce higher levels of apoptosis and cytotoxicity in low pH-adapted human melanoma cells than in cells grown at pH 7.3. DB-1 human melanoma cells, adapted to a tumour-like growth pH of 6.7, were exposed to hyperthermia (2h at 42 degrees C) and/or betulinic acid (4-10 microg/ml) and compared with cells grown at a physiological pH of 7.3 or after acute acidification from pH 7.3-6.3 or pH 6.7-6.3. Betulinic acid induced higher levels of apoptosis and cytotoxicity in low pH-adapted cells than in cells grown at pH 7.3, as measured by the terminal deoxynucleotidyl transferase (TdT) DNA fragmentation assay (TUNEL), the MTS cell viability assay, and single cell survival. Acute acidification of low pH adapted cells rendered them more susceptible to betulinic acid-induced apoptosis and cytotoxicity. In the presence of hyperthermia at 42 degrees C for 2 h, cells grown at pH 7.3 were not sensitized to heat killing by betulinic acid, whereas cells grown at pH 7.3 and acutely acidified to pH 6.3, cells adapted to growth at pH 6.7 and cells adapted to growth at pH 6.7 and acutely acidified to pH 6.3 were all similarly sensitized to heat killing by betulinic acid, with survival values of 5, 9 and 2%, respectively. It is concluded that betulinic acid may be useful in potentiating the therapeutic efficacy of hyperthermia as a cytotoxic agent in acidotic areas of tumours with minimal effect in normal tissues growing at pH 7.3.

Intracellular acidification of human melanoma xenografts by the respiratory inhibitor m-iodobenzylguanidine plus hyperglycemia: a 31P magnetic resonance spectroscopy study.

In vivo 31P magnetic resonance spectroscopy demonstrates that human melanoma xenografts can be significantly acidified by induction of hyperglycemia combined with administration of m-iodobenzylguanidine (MIBG), an inhibitor of mitochondrial respiration. In melanoma xenografts (< or =8 mm diameter), intracellular pH (pHi, measured by the chemical shift of the Pi resonance) and extracellular pH (pHe, measured with 3-aminopropylphosphonate) was reduced by less than 0.2 unit during i.v. infusion of glucose for 40 min. Administration of MIBG (30 mg/kg) under hyperglycemic conditions (26 mM) reduced tumor pHi and pHe by approximately 0.4 (P < 0.001) and approximately 0.6 (P < 0.001) unit, respectively; coincidentally, the nucleoside triphosphates:Pi ratio decreased approximately 60% (P < 0.004) relative to the baseline level. Minimal changes in pHi and pHe and a small decrease in nucleoside triphosphates:Pi ratio (26%, P = 0.2) were observed in liver in response to MIBG plus hyperglycemia. These results suggest that under normoglycemic and hyperglycemic conditions, small human melanoma xenografts (< or =8 mm) may exhibit a relatively high level of oxidative phosphorylation that may be blocked by MIBG. The acidification may result from increased lactate production as a direct effect of MIBG inhibition of respiration in mitochondria of tumor cells, or through indirect systemic effects, which remain to be identified. The synergetic effects of MIBG and hyperglycemia result in significant acidification of the tumor and a decrease in tumor bioenergetic status, and the effects are largely selective for tumors in comparison with normal tissues.

The response of human tumour blood flow to a fractionated course of thermoradiotherapy.

The response of human tumour blood flow to a fractionated course of thermoradiotherapy was documented in four superficial but bulky tumours (three adenocarcinomas, one melanoma). Blood flow was measured 15, 30, 45, and 60 min after the onset of heating. These measurements were made at the same intra-tumour point during each heat fraction by use of a modified thermal clearance technique in which a correction was made for the heat dissipated by thermal conduction. This point was at least 2 cm beneath the surface in the central portion of the tumour. Extracellular pH was measured within 1 cm of this point prior to the first heat fraction and 2-3 weeks later. Hyperthermia was administered for 60 min, twice a week for 4 weeks by use of a 16-channel 915 MHz microwave applicator. Each patient also received a radiation dose of 40 Gy fractionated at 2 Gy/fx, five times a week (adenocarcinomas) or 4 Gy/fx, twice a week (melanoma). Blood flow remained relatively constant during heating after steady state conditions were attained. However, an overall decrease in tumour blood flow was observed in each patient over the course of thermoradiotherapy. In each case, a relatively small decrease in blood flow occurred between most heat fractions which resulted in an overall decrease which ranged from 50-100%. However, there was a tendency for blood flow to increase following the initial heat fraction at points where the steady state temperature was approximately 41 degrees C or less. Extracellular pH increased in two of three patients and decreased in the other.

Effects of 42 degrees C hyperthermia on intracellular pH in ovarian carcinoma cells during acute or chronic exposure to low extracellular pH.

PURPOSE: To determine whether intracellular pH (pHi) is affected during hyperthermia in substrate-attached cells and whether acute extracellular acidification potentiates the cytotoxicity of hyperthermia via an effect on pHi. METHODS AND MATERIALS: The pHi was determined in cells attached to extracellular matrix proteins loaded with the fluorescent indicator dye BCECF at 37 degrees C and during 42 degrees C hyperthermia at an extracellular pH (pHe) of 6.7 or 7.3 in cells. Effects on pHi during hyperthermia are compared to effects on clonogenic survival after hyperthermia at pHe 7.3 and 6.7 of cells grown at pHe 7.3, or of cells grown and monitored at pHe 6.7. RESULTS: The results show that pHi values are affected by substrate attachments. Cells attached to extracellular matrix proteins had better signal stability, low dye leakage and evidence of homeostatic regulation of pHi during heating. The net decrease in pHi in cells grown and assayed at pHe = 7.3 during 42 degrees C hyperthermia was 0.28 units and the decrease in low pH adapted cells heated at pHe = 6.7 was 0.14 units. Acute acidification from pHe = 7.3 to pHe = 6.7 at 37 degrees C caused an initial reduction of 0.5-0.8 unit in pHi, but a partial recovery followed during the next 60-90 min. Concurrent 42 degrees C hyperthermia caused the same initial reduction in pHi in acutely acidified cells, but inhibited the partial recovery that occurred during the next 60-90 min at 37 degrees C. After 4 h at 37 degrees C, the net change in pHi in acutely acidified cells was 0.30 pH unit, but at 42 degrees C is 0.63 pH units. The net change in pHi correlated inversely with clonogenic survival. CONCLUSIONS: Hyperthermia causes a pHi reduction in cells which was smaller in magnitude by 50% in low pH adapted cells. Hyperthermia inhibited the partial recovery from acute acidification that was observed at 37 degrees C in substrate attached cells, in parallel with a lower subsequent clonogenic survival.

The development and magnitude of thermotolerance during chronic hyperthermia in murine granulocyte-macrophage progenitors: II.

We have previously reported that murine granulocyte-macrophage progenitors (CFU-GM) are capable of developing thermotolerance during chronic hyperthermia at temperatures of 40 to 42 degrees C. However, a differential profile of intrinsic thermal response and, in particular, the capability of developing thermotolerance during chronic heating was identified between CFU-GM and macrophage colony-forming units (CFU-M) stimulated respectively, by lung conditioned medium (LCM) and L929 cell conditioned medium (CCM). Nucleated marrow cells treated in vitro were cultured in McCoy's 5A medium plus 15% fetal bovine serum (FBS) in semisolid agar with 10% of CCM. Two different treatment protocols were used in this study to determine the kinetics of thermotolerance in CFU-M: (1) nucleated marrow from mouse tibia and femur were chronically heated in vitro at temperatures of 40, 41 and 42 degrees C (up to 480 min) or (2) nucleated marrow cells were heated over a period of 90 min stepwise from 37 to 42 degrees C, at a heating rate of 0.056 degrees C/min, before exposure to 42 degrees C. The amount of thermotolerance developed was analysed at various times after chronic incubation at 40-42 degrees C by a challenge with 15 min at 44 degrees C. In contrast to CFU-GM, the surviving fraction of CFU-M heated with 15 min at 44 degrees C did not increase during chronic hyperthermia at 40 degrees C for up to 480 min indicating failure to develop thermotolerance. However, CFU-M were able to develop thermotolerance during prolonged incubation at 41 and 42 degrees C, although to a much less extent than observed in CFU-GM. In other words, there was much less development of thermotolerance in murine CFU-M compared to that in CFU-GM. Furthermore, a slow temperature transit from 37 to 42 degrees C over 90 min before exposure to 42 degrees C induced CFU-M to develop thermotolerance. The thermotolerance ratio (TTR, the ratio of the surviving fraction at maximum tolerance versus normotolerance) increased from a maximum of 3.5 after 180 min at 42 degrees C (no warm-up) to a maximum of 4.1 after 60 min at 42 degrees C when the cells received a slow warm-up to 42 degrees C. This implies that in the murine bone marrow granulocyte/macrophage lineage, CFU-M does not normally develop thermotolerance during hyperthermia and that the colony forming unit-granulocyte (CFU-G) and CFU-GM play a more critical role than CFU-M in the initiation and promotion of thermotolerance during chronic hyperthermia. However, in a situation that simulates the slow heat-up used clinically in wholebody hyperthermia, e.g., the 90 min slow warm-up from 37 to 42 degrees C, stimulated CFU-M to develop greater thermotolerance more rapidly than during rapid heating.

The development and magnitude of thermotolerance during chronic hyperthermia in murine bone marrow granulocyte-macrophage progenitors: I.

Murine bone marrow granulocyte-macrophage progenitors (CFU-GM) are capable of developing thermotolerance during exposure to temperatures < 42.5 degrees C. Bone marrow from the tibia and femora was heated to 40-42 degrees C (i.e. chronic hyperthermia), and challenged immediately with 15 min at 44 degrees C at regular intervals during treatment (step-up heating). CFU-GM were heated and cultured in McCoy's 5A medium + 15% FBS (fetal bovine serum) and lung-conditioned medium (source of colony stimulating factor) in semisolid agar. The kinetics of thermotolerance development and decay, and the magnitude of the thermotolerance during chronic heating with temperatures of 40-41.5 degrees C were similar. Survival increased rapidly to a maxima by approximately 120 min of hyperthermia (temperatures of 40-41.5 degrees C) and thereafter decreased with a slope similar to the controls. Normalization for cell killing by chronic hyperthermia that occurred during "step-up' heating permitted analysis of thermotolerance in the surviving cells. The surviving fraction after 15 min at 44 degrees C, during incubation at 40, 41 and 41.5 degrees C increased from 0.13 to maxima of 0.56 +/- 0.04, 0.71 +/- 0.03 and 0.82 +/- 0.03 respectively, by 150 min and did not decrease for up to 480 min during chronic hyperthermia. The surviving fraction after 15 min at 44 degrees C during incubation at 42 degrees C increased more slowly than during incubations at 40-41.5 degrees C. The survival of thermotolerant cells after exposure to 15 min at 44 degrees C during 42 degrees C chronic hyperthermia was maximal at 0.87 +/- 0.08 by 120 min and then decreased after approximately 150 min of exposure to 42 degrees C. The thermotolerance ratios (TTR's) were 4.0, 5.4, 6.7 and 6.9 for temperatures of 40, 41, 41.5 and 42 degrees C respectively. The results suggest that chronic hyperthermia temperatures (i.e. 40-42 degrees C) induce rapid thermotolerance development in CFU-GM during the thermal exposure and protect this normal marrow progenitor during whole body hyperthermia or ex vivo purging of leukaemic cells.

Predictive factors for skin reactions in patients treated with thermoradiotherapy.

In this study we performed univariate analyses to analyse the predictive factors for skin reactions, i.e. erythema, thermal blisters and ulceration, that occur during thermoradiotherapy. One hundred and twenty-six fields in 126 patients were treated with thermoradiotherapy using 915 MHz external microwave hyperthermia. Mean age of patients was 62 years. All but 11 lesions received previous therapy. Prior treatment included surgery (75%), chemotherapy (60%) and/or radiation therapy (51%). The mean previous radiation dose was 54 +/- 2 Gy. The concurrent tumour radiation dose was 45 +/- 1 Gy, in 16 fractions, over 35 elapsed days (dose per fraction of 1.6-4.8 Gy). The mean number of heat sessions administered was 5.5 +/- 0.2 (range 1-14). In 83% of cases hyperthermia was administered biweekly. Forty-two patients were treated without any skin reaction (33%), erythema occurred in 59 fields (47%), transient thermal blisters occurred in 25 fields (20%) and ulceration occurred in 23 fields (18%). In 25 cases, two or more skin reactions (20%) were observed concurrently. Concurrent radiation dose correlated with skin reactions (p = 0.02). The incidence of skin reactions was inversely correlated with previous radiation therapy (p = 0.04) and previous radiation therapy dose (p = 0.04) possibly due to fibrosis. None of the tumour or skin thermal parameters correlated with the reaction rate.

Extracellular pH distribution in human tumours.

Extracellular pH (pHc) was determined by needle microelectrodes in 67 tumour nodules in 58 patients. The objective was to evaluate the relationship between pHe, tumour histology and tumour volume. The mean age of the patients was 62 years, mean depth of the lesions was 2.7 +/- 0.2 cm, and mean tumour volume was 187 +/- 60 cm3. Lesions were located in readily accessible areas such as on the limbs, neck or chest wall. Tumour histologies included: 48% adenocarcinoma; 34% squamous cell carcinoma; 8% soft tissue sarcoma; and 10% malignant melanoma. The mean tumour pHe for the entire group of tumours was 7.06 +/- 0.05 (range 5.66-7.78). Variation in pHe measurements between tumours was greater than the variation in measurements within tumour (F = 7.11, p < 0.01). In adenocarcinomas pHe was 6.93 +/- 0.08 (range 5.66-7.78), in soft tissue sarcomas 7.01 +/- 0.21 (6.25-7.45), in squamous cell carcinomas 7.16 +/- 0.08 (6.2-7.6), and in malignant melanomas 7.36 +/- 0.1 (6.98-7.77). Tumour pHe was significantly different between the four histological groups (p < 0.001). When adenocarcinoma and soft tissue sarcoma lesions were grouped together, pHe was 6.94 +/- 0.08 compared with 7.20 +/- 0.07 in squamous cell carcinomas and malignant melanomas lesions (p < 0.01). Tumour pHe increased as a function of the logarithm of tumour volume at 0.07 +/- 0.02 pH unit/ln cm3 (p = 0.006, r = 0.34). In conclusion, tumour histology and tumour volume were the most important factors determining the range of pHe's.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermoradiotherapy in the management of superficial malignant tumors.

In recent years there have been numerous randomized and nonrandomized studies conducted to assess the efficacy of hyperthermia combined with either radiation therapy or chemotherapy, especially in the treatment of superficially seated malignant tumors. The major impact of hyperthermia is currently on locoregional control of tumor. Heat may be directly cytotoxic to tumor cells or inhibit repair of both sublethal and potentially lethal damage after radiation. These effects are augmented by the physiological conditions in tumors which lead to states of acidosis and hypoxia. Blood flow is often impaired in tumor relative to normal tissue, and hyperthermia may lead to a further decrease in blood flow and augment heat sensitivity. Three major areas of clinical investigation have borne the greatest fruit for hyperthermia as adjunctive therapy to radiation therapy. These include recurrent and primary breast lesions, melanoma, and head and neck neoplasms. The thermal enhancement ratio was increased in all cases and is estimated to be 1.4 for neck nodes, 1.5 for breast, and 2 for malignant melanoma. In general, the most important prognostic factors for complete response are radiation dose, tumor size, and minimal thermal parameters (minimum thermal dose, mean minimum temperature or temperature exceeded by 90% of thermal sensors). The number of heat fractions administered per week appears to have no bearing on the overall response, which may be indicative of the effects of thermotolerance. The total number of heat fractions delivered also appears to be irrelevant provided adequate heat is delivered in one or two sessions. The major prognostic factors for the duration of local control are tumor histology, concurrent radiation therapy dose, tumor depth, and mean minimum temperature.

Thermal response and hyperthermic radiosensitization of scid mouse bone marrow CFU-C.

PURPOSE: Scid mice are severely immunodeficient as a result of a defective recombinase system. Mice with the scid mutation have been shown to have an increased sensitivity to ionizing radiation, presumably as a result of an inability to repair DNA damage. Little is known of the impact of this mutation on the thermal response and on hyperthermic radiosensitization. This investigation established the thermal response (42-44 degrees C), patterns of thermotolerance development, and the impact of hyperthermia (60 min at 40 degrees C or 42 degrees C) on the radiation response of bone marrow colony forming unit-culture cells (CFU-C) in scid mice. METHODS AND MATERIALS: Anesthetized scid mice (pentobarbital, 90 mg/kg) were killed by cervical dislocation and the nucleated marrow obtained from both tibia and femora by passing 2 ml of cold McCoy's 5A medium supplemented with 15% fetal bovine serum through each bone. Single cell suspensions of nucleated marrow were heated in 12 x 75 mm sterile tissue culture tubes at a concentration of approximately 5 x 10(6) cells/ml. Radiation, when used, was delivered immediately prior to hyperthermia by a 137Cs irradiator (dose rate of 1.20 Gy/min). Colony forming unit-culture were cultured in semisolid agar in the presence of colony stimulating factor (conditioned medium from L929 cells) for 7 days. RESULTS: The slope of the radiation dose-response curve for CFU-C in scid mice was biphasic, the Dos (+/- SE) were 0.29 +/- 0.03 Gy and 1.09 +/- 0.20 Gy, respectively. The Dos of the radiation dose-response curve for wild type marrow from CB-17 and Balb/c mice were 1.28 +/- 0.05 Gy and 1.47 +/- 0.15 Gy, respectively. The Dos of the hyperthermia dose-response curves for scid mice were 75 +/- 5, 10 +/- 1.4, and 4 +/- 0.2 min, respectively, for temperatures of 42 degrees, 43 degrees, and 44 degrees C. Thermotolerance development at 37 degrees C increased to a maximum at approximately 240 min after acute hyperthermia (15 min at 44 degrees C) and thereafter, decreased to control levels within 15 h. Thermotolerance did not develop in scid CFU-C during chronic hyperthermia at temperatures < 42.5 degrees C. Hyperthermia (60 min at 40 degrees or 42 degrees C) immediately after ionizing radiation did not significantly alter the terminal slope of the radiation dose-response curve of scid CFU-C (Do = 1.28 +/- 0.08 Gy). By contrast, hyperthermia following radiation of wild type CFU-C resulted in a decrease in the Do from 1.47 +/- 0.05 Gy (Balb/c, rad only) to 1.31 +/- 0.08 or 1.06 +/- 0.18 Gy for 60 min at 40 degrees or 42 degrees C, respectively. CONCLUSION: These results show that the thermal response and the pattern of thermotolerance development of scid CFU-C were similar to that of wild type Balb/c CFU-C, but that hyperthermia given immediately after ionizing radiation did not alter the radiation response of scid CFU-C. The scid mutation does not increase hyperthermic sensitivity or change the pattern of thermotolerance development of scid mouse CFU-C, implying that the scid mutation is not involved with thermal response, but does render the already radiation-sensitive scid cells incapable of thermal radiosensitization.

Multiple field hyperthermia combined with radiotherapy in advanced carcinoma of the breast.

Extensive recurrences on the chest wall of advanced carcinoma of the breast in 20 patients were treated with multiple field patchwork hyperthermia combined with radiation therapy between 1987-1991. The objective of the study was to evaluate the feasibility, tumour response and complications of treating extensive lesions with multiple, overlapping fields of hyperthermia. All lesions were diffuse encompassing up to 2900 cm2 in area with or without multiple nodules < or = 3 cm deep. All lesions had failed previous therapy with all but three failing previous radiotherapy. Hyperthermia consisted of 282 hyperthermia applicator fields and 357 hyperthermia treatments with external 915 MHz microwaves using commercially available applicators. Hyperthermia applicator fields were defined by the surface 50% SAR distribution of a particular applicator, and hyperthermia fields were abutted to cover the entire tumour bearing area. Radiation therapy consisted of 81 fields to a mean dose of 40 +/- 1 Gy (SE), 88% of fields received between 30 and 50 Gy. The equivalent dose was 42 +/- 1 Gy, based on the linear-quadratic model and alpha/beta = 25 (Fowler 1989). Overlapping hyperthermia fields were separated by an interval of at least three days. Up to four heat sessions per week were required to cover the entire tumour in a rotating fashion. The hyperthermia treatment time was 60 min. Hyperthermia treatments were continued for the duration of radiation therapy. Each hyperthermia applicator field was heated at least once. Patients were exposed to a mean of 14 +/- 3 hyperthermia applicator fields (range of 3-46 fields) and a mean of 18 +/- 3 hyperthermia treatments (range of 6-61) delivered over a mean of 7.5 +/- 0.9 weeks (range of 3-17 weeks). Each field was heated an average of 1.3 times. The tumour complete response rate was 95% with a recurrence rate of 5%. Nevertheless, the mean survival of patients with a complete response was only 10.8 +/- 1.7 months (range of 2-28 months) because of the systemic tumour burden existing outside of the treated fields in these patients. Neither complete response, local control nor survival after thermoradiotherapy correlated with the disease free interval between initial mastectomy and recurrence. There was no evidence of increased thermal damage to skin nor evidence of tumour recurrence at junctions of hyperthermia field overlap. It is concluded that recurrent advanced carcinoma of the breast presenting as extensive, diffuse lesions on the chest wall can be treated as effectively with multiple field patchwork thermoradiotherapy as can nodular lesions treated with single hyperthermia fields.

Tumor extracellular pH as a prognostic factor in thermoradiotherapy.

PURPOSE: Tumor extracellular pH measurements in 26 human tumors were evaluated for the purpose of prognostic indication of response to thermoradiotherapy. METHODS AND MATERIALS: Twenty-six patients (10 male, 16 female; mean age 62 years, range 18-89) were treated with external microwave hyperthermia (915 MHz) combined with radiation therapy. Tumor histologies included: 46% adenocarcinoma, 38% squamous cell carcinoma, 12% soft tissue sarcoma, and 4% malignant melanoma. The mean tumor depth was 1.6 +/- 0.2 cm (range 0.4-3 cm) and the mean tumor volume was 73 +/- 11 cm3 (range 1-192 cm3). The mean radiation dose administered concurrently with hyperthermia was 39 +/- 1 Gy (range 24-60 Gy, median of 40 Gy), in 15 fractions (range 8-25), over 32 elapsed days (range 15-43). The mean number of hyperthermia sessions administered was 5.4 +/- 0.5 (range 2-10). A battery operated pH meter and combination 21 ga recessed glass, beveled needle microelectrodes were used for tumor pH measurements. Calibration in pH buffers was performed before and after each pH measurement. The needle microelectrodes were 2.5 cm in length. RESULTS: A complete response (CR) was obtained in 20 of 26 patients (77%) and a partial response in six (23%). The mean extracellular tumor pH was 6.88 +/- 0.09 in CR patients while it was 7.24 +/- 0.09 in noncompletely responding (NCR) patients (p = 0.08). Logistic regression analysis indicated that the probability of obtaining a complete response was influenced by the tumor volume (p = 0.02), tumor depth (p = 0.05), and extracellular tumor pH (p = 0.08). Lesions in the pH range of 6.00-6.40 and lesions in the pH range of 6.41-6.80 exhibited a CR rate of 100%, while those lesions in the pH range of 6.81-7.20 exhibited a CR of 90% and those in the pH range of 7.21-7.52 exhibited a CR of 50% (p = 0.002). In lesions with depth < or = 1.5 cm, the CR rate was 100% when the tumor pH was < 7.15 and 75% when the tumor pH was > or = 7.15. In lesions with depth between 1.5 and 3 cm, the CR rate was 66% when the tumor pH was < 7.15 and 43% when the tumor pH was > or = 7.15 (p = 0.02). In small tumors, that is, < or = 20 cm3, tumor pH increased with volume, whereas in larger tumors, that is, > 20 cm3, tumor pH decreased as a function of tumor volume. CONCLUSION: Tumor extracellular pH may be useful as a prognostic indicator of tumor response to thermoradiotherapy.

Thermoradiotherapy for superficial tumour deposits in the head and neck.

Tumour deposits in the head and neck region were treated with hyperthermia using 915 MHz external microwave applicators and radiation therapy between 1986 and 1990. The mean (+/- SE) radiation dose was 47 +/- 2 Gy (range 21-77 Gy). All but four patients had failed previous therapy. Mean tumour volume was 40 +/- 10 cm3 (range 0.3-276 cm3). Hyperthermia was administered biweekly in 80% of the patients in 6.0 +/- 0.4 sessions (range 1-10); thermometry involved 3.6 +/- 0.4 catheters (range 1-9) and 5.7 +/- 0.4 sensors (range 1-12) per tumour. Of the 50 lesions evaluable for response, 29 had a complete response (58%), and 20 had a partial response (40%). Lesions were stratified by depth. In tumours considered potentially heatable (i.e. depth < or = 3 cm and lateral dimensions at least 2 cm less than boundary of applicator), the complete response rate was 81% (26/32, 47 +/- 2 Gy, 15 +/- 3 cm3); whereas for patients with tumours deeper than 3 cm, the complete response rate was 17% (3/18, 48 +/- 3 Gy, 110 +/- 21 cm3), p = 0.0001. Among lesions < or = 3 cm depth that exhibited a complete response, six recurred (24%, 5.8 +/- 1.8 months) while 20 lesions were recurrence free at last follow-up of 11.9 +/- 1.2 months). The overall survival of patients with lesions < or = 3 cm depth was 11.5 +/- 1.3 months (range 2.4-32.3 months) while for patients with lesions > 3 cm depth survival was 6.7 +/- 0.9 months (range 2.1-18.6 months), p = 0.01. In superficial lesions with depth < or = 3 cm, multivariate logistic regression analysis indicated that the model best correlating with complete response included radiation dose (p = 0.08) and tumour volume (p = 0.08, model p = 0.004). Multivariate proportional hazard analysis indicated that the model best correlating with duration of local control included tumour depth (p = 0.03) and previous radiation therapy (p = 0.08, model p = 0.006). Twenty-two fields were treated without any skin reactions (39%), 23 evidenced erythema (40%) and eight thermal blistering (14%). Ulceration occurred in 11 treatment fields but in all but one of these cases the ulceration may have been due to tumour breakdown as there was direct invasion of the skin by tumour prior to the initiation of treatment. The maximal skin temperature was the best predictor of morbidity although the correlation was not statistically significant (p = 0.19).

'Patchwork' fields in thermoradiotherapy for extensive chest wall recurrences of breast carcinoma.

Chest wall lesions of advanced breast carcinoma in 23 patients were treated with thermoradiotherapy with clinical intent between January 1987 and March 1992. Treatment consisted of external 915 MHz microwave hyperthermia with commercially available applicators and radiation therapy to doses between 32-58 Gy. Twenty-three large, diffuse lesions were treated with multiple field patchwork hyperthermia. All lesions were diffuse with or without multiple nodules < or = 3 cm depth. All lesions had failed previous therapy. The mean number of hyperthermia fields per patient was 3.2 +/- 0.4 (range of 2-7). The complete response rate was 91% in this group of extensive, diffuse lesions treated by the patchwork technique. Mean total radiation dose administered concurrently with multiple field patchwork hyperthermia was 42 +/- 1 Gy. The recurrence rate was 5%. The mean survival in patients who had a complete response was 9.0 +/- 1.3 months. The reduced survival among patchwork treated patients was due to the extensive tumor burden existing outside of the treated fields in these patients. The skin reactions were minor, causing minimal discomfort. There was no evidence of increased thermal damage to skin, or of tumor recurrence at junctions of hyperthermia field overlap. It is concluded that extensive, diffuse lesions of chest wall recurrence of advanced carcinoma of the breast can be treated effectively with multiple field patchwork thermotherapy.

Thermoradiotherapy with combined interstitial and external hyperthermia in advanced tumours in the head and neck with depth > or = 3 cm.

Advanced tumours in the head and neck 3-6 cm depth are too deep to be completely heated by external 915 MHz microwaves. A preliminary study was performed using interstitial plus external hyperthermia combined with external beam radiation therapy to heat tumours to depths > or = 3 cm. Nine advanced metastatic lesions of squamous cell carcinoma located in the head and neck were treated between 1987 and 1990 with the combined hyperthermia technique and radiation doses of 38-60 Gy (mean of 49 +/- 3 Gy). The mean tumour volume was 58 +/- 9 (SE) cm3 (range 24-94 cm3) with a mean tumour depth of 3.9 +/- 0.3 cm (range 3-5.5 cm). The deeper aspects of the tumour were heated by interstitial 915 MHz microwave antennas and the superficial aspects heated by external 915 MHz applicators. A single plane of polyurethane closed-end catheters, 16 Ga, were inserted under local anaesthesia approximately 1.5-2 cm apart in parallel arrays at the base of a lesion behind the sternomastoid muscle, or an equivalent site in a dissected neck, extending forward and angled deeply no more than 15 degrees. Hyperthermia was administered twice weekly immediately after radiation therapy in a mean of 5.3 +/- 0.7 external heat sessions (range 3-7) and a mean of 3.5 +/- 0.6 interstitial heat sessions (range of 1-6). Interstitial hyperthermia was usually administered in alternating sessions with external hyperthermia, but in some patients all of the sessions of one modality were administered followed by all of the sessions of the other modality. In no case were both interstitial and external heatings performed on the same day. Surface thermometers were used to monitor skin temperature during external hyperthermia sessions. Results showed that by 8 weeks after completion of treatment, six lesions exhibited a complete response (67%) and three a partial response (33%). One of the partial responses continued to regress and became a complete response (78% complete response). The recurrence rate in complete responders was 14% (1/7) with time to recurrence of 7.7 months. Six lesions were recurrence-free at last follow-up of 21.3 +/- 8.8 months. Skin reactions were absent in four fields (44%), erythema was noted in five (56%) and thermal blistering in one (11%). Ulceration occurred only in association with tumour breakdown when the skin was infiltrated by tumour (three patients, 33%).(ABSTRACT TRUNCATED AT 400 WORDS)

Thermoradiation therapy for superficial malignant tumors.

BACKGROUND: Between 1980-1990, 126 patients were treated with radiation therapy (RT) and hyperthermia using 915-MHz external microwave applicators. All but 11 patients had failed to respond to previous therapy. METHODS: The mean tumor volume was 73 +/- 13 cm3, and the mean radiation dose delivered was 45 +/- 1 Gy. Hyperthermia was administered biweekly in 83% of the fields in 5.5 +/- 0.2 sessions. Lesions were stratified by depth. The predictive influence of pretreatment or treatment parameters was analyzed for the probability of response by logistic regression and for the duration of local control by proportional hazards. RESULTS: In tumors considered potentially heatable (i.e., < or = 3-cm deep), the complete response (CR) rate was 70%, whereas the CR rate for patients with tumors deeper than 3 cm was 18% (P < 0.0001). Among superficial lesions of less than or equal to 3-cm depth that exhibited a CR, 14 recurred (26%, 8.7 +/- 1.6 months), while 39 lesions were recurrence-free at last follow-up of 17.8 +/- 1.4 months. The 50% tumor-effective dose was 44 Gy. For superficial lesions that received between 30-60 Gy, the CR rate was 55% when the fraction size was less than 3 Gy, whereas it was 77% when the fraction size was 3-4 Gy (P = 0.05). Multivariate logistic regression analysis indicated that the model best correlating with CR included concurrent radiation dose (P = 0.006) and tumor volume (P = 0.02; model P = 0.0001). Multivariate proportional hazard analysis indicated that the model best correlating with duration of local control included tumor histology (P = 0.004; model P = 0.0007). The overall survival rate of patients with lesions of less than or equal to 3-cm depth who were treated with thermoradiation therapy was 16.1 +/- 1.2 months. For patients with lesions more than 3-cm deep, survival was 8.7 +/- 1.1 months (P < 0.001). Forty-two fields were treated without any skin reactions (33%), 59 exhibited erythema (47%), and 25 experienced thermal blistering (20%). CONCLUSIONS: Treatment of superficial malignant tumors can benefit from the adjuvant use of hyperthermia delivered with external 915-MHz applicators provided tumors are less than 3 cm from the surface and the lateral margins are within the 50% specific absorption rate (SAR) on the surface.